1. Field of the Invention
The present invention relates to a medical guide wire. More particularly, the present invention relates to a medical guide wire for use in treatment of blood vessels of constriction, for example a coronary artery, an artery of lower extremities or the like.
2. Description Related to the Prior Art
A medical guide wire is used for inserting a catheter into a blood vessel for various purposes. A flexible catheter of a very small width is inserted with the medical guide wire for the purpose of angiography of vessels. Otherwise, a balloon catheter is inserted in an occlusion of a coronary artery for intravascular treatment. The use of the medical guide wire is for safety and reliability. The medical guide wire is required to have flexibility and buckling resistant property for the purpose of insertion in vessels of complicated curved paths or vessel branches. Also, the medical guide wire should have steerability and suitable rigidity of torsion in order to operate the guide wire tip in a vessel by extracorporeally rotating the proximal end of the medical guide wire. JP-U 59-016649 and U.S. Pat. No. 5,354,257 (corresponding to JP-A 4-309368) disclose the medical guide wire including a core and a helical coil. The core has a very small diameter. The helical coil is wound about the core, has a decreasing diameter, so the guide wire tip of the medical guide wire has a tapered shape.
In FIG. 12, a total occlusive lesion 100 in a coronary artery is illustrated. According to gradual organization of thrombus, an occlusion 102 in a blood vessel 101 becomes tissue. Organization is rather early on ends of the occlusion 102 in contrast with slowness in organization at the middle point of the occlusion 102. As a result, portions of plaque or hard tissue 103 occur in the middle path in the blood vessel 101. For the total occlusive lesion 100, a medical guide wire 105 for intravascular treatment is used to penetrate the total occlusive lesion 100 by rotating forwards and backwards, the medical guide wire 105 including a flexible helical coil disposed at the guide wire tip, and having strands spaced from one another.
When the guide wire tip of the medical guide wire 105 is rotated forwards and backwards, a cavity called a false lumen 106 is created in a different direction by drilling of the medical guide wire 105. The false lumen 106 may be enlarged, from which the medical guide wire 105 cannot move away. A true lumen cannot be reached as intended in the vessel. In FIG. 13, a recently used method of penetration of the total occlusive lesion 100 is illustrated. A medical guide wire 110 for intravascular treatment has a rigid tip, and can penetrate the total occlusive lesion 100 even with the plaque or hard tissue 103 contained in the total occlusive lesion 100. Conception of improving the medical guide wire 110 has been developed in view of suitability for this method. If the rigidity of the guide wire tip is too high, steerability of the medical guide wire 110 will be low because of low flexibility of the guide wire tip.
In FIG. 14, an encircling calcified lesion 115 is created as a result of organizing thrombus. Plaque or hard tissue 116 of the calcified lesion 115 is still more difficult to penetrate with a tool. There a pair of ends 118 and 119 in a cup shape disposed on the sides of the occlusion of the calcified lesion 115. The end 118 has a greater thickness than the end 119. When a medical guide wire 120 for intravascular treatment passes through the blood vessel, the guide wire tip buckles in the vicinity of the end 118, which cannot be penetrated. If the medical guide wire 120 can penetrate, the guide wire tip is likely to offset from the middle of the end 119. The guide wire tip may erroneously reach a false lumen 121, because the middle of the end 119 is convexly formed. No known structure of the guide wire tip can penetrate successfully.